Which finding best describes Wartenberg's sign?

Which finding best describes Wartenberg's sign?

• A. Involuntary abduction of the 5th digit
• B. Hyperextension of the thumb
• C. Inability to extend the index finger
• D. Loss of sensation on the palm

Answer: (A)

Wartenberg sign reflects loss of control over the little finger due to ulnar nerve weakness. When someone tries to bring the pinky toward the ring finger (adduct the fifth digit), the finger instead drifts away and stays in an abducted position because the muscle that normally pulls it inward, the adductor digiti minimi, is not working. The little finger’s abduction is unopposed by the weak intrinsic muscles, so you observe involuntary abduction of the fifth digit. This motor sign points specifically to ulnar nerve palsy and helps distinguish it from other nerve injuries that primarily affect sensation or other fingers. The other options describe different functions: hyperextension of the thumb isn’t tied to this sign, inability to extend the index finger involves different extensors, and loss of sensation on the palm indicates sensory loss rather than the motor drift seen in Wartenberg sign.

Wartenberg sign reflects loss of control over the little finger due to ulnar nerve weakness. When someone tries to bring the pinky toward the ring finger (adduct the fifth digit), the finger instead drifts away and stays in an abducted position because the muscle that normally pulls it inward, the adductor digiti minimi, is not working. The little finger’s abduction is unopposed by the weak intrinsic muscles, so you observe involuntary abduction of the fifth digit. This motor sign points specifically to ulnar nerve palsy and helps distinguish it from other nerve injuries that primarily affect sensation or other fingers. The other options describe different functions: hyperextension of the thumb isn’t tied to this sign, inability to extend the index finger involves different extensors, and loss of sensation on the palm indicates sensory loss rather than the motor drift seen in Wartenberg sign.